/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.reactive.result.method.annotation;

import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.core.MethodParameter;
import org.springframework.core.ReactiveAdapter;
import org.springframework.core.ReactiveAdapterRegistry;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.web.bind.annotation.RequestAttribute;
import org.springframework.web.bind.annotation.ValueConstants;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.ServerWebInputException;
import reactor.core.publisher.Mono;

/**
 * Resolves method arguments annotated with an @{@link RequestAttribute}.
 *
 * @author Rossen Stoyanchev
 * @see SessionAttributeMethodArgumentResolver
 * @since 5.0
 */
public class RequestAttributeMethodArgumentResolver extends AbstractNamedValueSyncArgumentResolver {


    /**
     * Create a new {@link RequestAttributeMethodArgumentResolver} instance.
     *
     * @param factory  a bean factory to use for resolving {@code ${...}}
     *                 placeholder and {@code #{...}} SpEL expressions in default values;
     *                 or {@code null} if default values are not expected to have expressions
     * @param registry for checking reactive type wrappers
     */
    public RequestAttributeMethodArgumentResolver(@Nullable ConfigurableBeanFactory factory,
                                                  ReactiveAdapterRegistry registry) {

        super(factory, registry);
    }


    @Override
    public boolean supportsParameter(MethodParameter param) {
        return param.hasParameterAnnotation(RequestAttribute.class);
    }


    @Override
    protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
        RequestAttribute ann = parameter.getParameterAnnotation(RequestAttribute.class);
        Assert.state(ann != null, "No RequestAttribute annotation");
        return new NamedValueInfo(ann.name(), ann.required(), ValueConstants.DEFAULT_NONE);
    }

    @Override
    protected Object resolveNamedValue(String name, MethodParameter parameter, ServerWebExchange exchange) {
        Object value = exchange.getAttribute(name);
        ReactiveAdapter toAdapter = getAdapterRegistry().getAdapter(parameter.getParameterType());
        if (toAdapter != null) {
            if (value == null) {
                Assert.isTrue(toAdapter.supportsEmpty(),
                        () -> "No request attribute '" + name + "' and target type " +
                                parameter.getGenericParameterType() + " doesn't support empty values.");
                return toAdapter.fromPublisher(Mono.empty());
            }
            if (parameter.getParameterType().isAssignableFrom(value.getClass())) {
                return value;
            }
            ReactiveAdapter fromAdapter = getAdapterRegistry().getAdapter(value.getClass());
            Assert.isTrue(fromAdapter != null,
                    () -> getClass().getSimpleName() + " doesn't support " +
                            "reactive type wrapper: " + parameter.getGenericParameterType());
            return toAdapter.fromPublisher(fromAdapter.toPublisher(value));
        }
        return value;
    }

    @Override
    protected void handleMissingValue(String name, MethodParameter parameter) {
        String type = parameter.getNestedParameterType().getSimpleName();
        String reason = "Missing request attribute '" + name + "' of type " + type;
        throw new ServerWebInputException(reason, parameter);
    }

}
